Catalytic conversion of hydrocarbon oils



vcz. E. HEMMINGER CATALYTIC 4CNVERSION 0F HYDROCARBON OILS Y Filed sept.12 191,11

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Patented July 3,- 1.945

CATALYTIC CONVERSION F HYDRO- CARBON OILS Charles E. Hemmingen',Westield, N.

J., assigner to Standard Oil Development Company, a corporation ofDelaware Application September 12, 1941, Serial No. 410,526 4 Claims.(Cl. 19E-52) This invention relates to the catalytic cracking ofhydrocarbon oils and pertains more particularly to a `process ofcracking heavy oils, such as heavy gas'oilsgreduced crudes or otherheavy oils, into motor fuels in the presence of a catalyst infinely-divided form.

Heretofore it has been proposed to crack oils in the presence of acracking catalyst to form gasoline of relatively high octane rating.According to one general mode of operation, the oil in dry vapor form ispassed through a. cracking zone containing a xed mass of catalyst in theform of a single bed or a plurality of beds suspended upon trays locatedwithin the cracking chamber.

During the cracking process vthe activity of the catalyst rapidlydepreciates due to the formation of carbonaceous deposits which accumu-Vlate on the catalyst. In view of this, it is necessary to interrupt thecracking process frequently and regenerate the catalyst :by burning thecarbonaceous deposits therefrom.

In order toreduce the amount of canbonaceous deposits formed on thecatalyst during the cracking period, it has been the practice in suchcases to pass a relatively dry vapor in contact with the catalyst. Forexample, the general procedure in such processes is to rst pass the oilto be cracked through a vaporizing coil lto vaporize the bulk of the oiland then to pass the products from the vaporizing coil to a separator soas to segregate the vapors formed from any unvaporized residue.Following this, the vapors are passed through a superheating furnacewherein the oil is heated to a temperature materially above its dewpoint and the superheatedvapors then pass to the cracking zone wherethey are contacted with the catalyst contained therein. Expressed inother words, it has been the practice heretofore to avoid contacting thecatalyst with any liquid oil so as to avoid the accumulation ofexcessive deposits during the cracking operation. v

This method of operating not only requires considerahle investment inpreheating, vaporizing and separating equipment; for the preparation ofthe feed for the catalytic process but, in cases 'of residual stockssuch as topped or reduced crudes, it also requires the rejection of aresidual fraction which is not suitable Afor catalytic cracking withoutfurther processing. This fraction may comprise from 5% to 25% or more ofthe original crude, depending upon the source and nature thereof. Whileit has been suggested heretofore to subject this residual fraction tofurther processing, such as a viscosity breaking or coking treatment torecover additional vaporizable Aoil for the catalyst cracking' process,such treatment results in the production, of substantial quantities oflow-grade gasoline. In view of this, it is a practice in many cases tomarket the residual fractionas a fuel rather than attempt to recover anyadditional motor fuel therefrom.

One of the principal objects of thepresent invention is to provide animproved process for the production of motor fuel which will reduce the`amount of equipment necessary for a catalytic In the past it hasfrequentlybeen desirable to crack catalytically relativelyv heavydistillates, such as heavy oils obtained from'distillation of pitches,tars and the like, or from coking processes in which said heavy residuesare converted into a solid `coke residue. To utilize these heavy oils asa, stock for catalytic cracking processes, it has ybeen necessary in thepast to either distill them under a high vacuum, which is uneconomical,or to employ relatively large volumes of steam to effect thevaporization. The presence of steam in the products to be crackedreduces the capacity of the equipment, or, expressed in another way,increases the size of the cracking and fractionating equipment for acracking plant of given capacity.

I have discovered that the catalytic cracking process can be carried outwithout excessive formation of low-grade products, such as coke and gas,without completely vaporizing the oil. This discovery makes it possibleto employ as feed stock for the catalyticcracking process not only heavycondensates but permits the use of residual stocks which cannot bereadily vaporized without substantial decomposition and which could notheretofore be used for catalytic cracking.

In accordance with the present invention, an adsorptive crackingcatalyst in nely-divided form is rst suspended in a gas or vapor stream.Following this, a hydrocarbon oil to be cracked, either in liquid phaseor in a mixed phase con- Vtaining a substantial amount of liquid, iscombined with the suspension and the resulting mixture subjected tocracking conditions of time and temperature to obtain the desiredconversion. The gas stream into which the catalyst is suspended maycomprise oil vapors to be cracked, natural gas, refinery gas obtainedfrom the same or different cracking unit, or it may be a relativelyinert gas from an extraneous source, such as steam, nitrogen, hydrogen,carbon dioxide, spent combustion gases, or the like. l

Having set forth the general nature and objects, the invention will bebetter understood from the following descriptionv in which referencewill be made to the accompanying drawing which is a diagrammaticillustration of an apparatus capable of carrying the invention intoeffect.

Referring to the drawing, the reference character III designates acharge line into which the oil to be processed is introduced into thesystem. For illustrative purposes, equipment has been shown for treatinga total crude which may contain straight-run gasoline or otherlow-boiling distillates which are not to be utilized as crack-y ingstock for the catalytic cracking process. The crude introduced throughline I is pumped by means of pump II through a preheating coil I2located in furnace I3 in which the oil is heated to a temperaturesuiiicient to..vaporize the lowboiling distillate fractions of the crudewhich are to be removed from the oil before passing the. same to thecracking process.l For example, the oil during its passage through thepreheating coil I2 may be heated to a temperature of the order of from400 F. to 600 F. The heated oil after passing through the coil I2discharges into a separator I4 in which heating treatment separate fromunvaporized residue. Vapors liberated in the separator I4 pass overheadthrough line I5 to a. condenser I6 in which the normally liquid productsare condensed. Products from the condenser IG'then discharge into aproduct receiver l1 from which the liquid distillate is removed throughline I8. Any normally gaseous constituents liberated during thedistillingoperation may be removed from the receiver I1 through line I9.

As previously mentioned, the distillate removed overhead from theseparator I4 may comprise a straight-run gasoline from the originalcrude, or it may consists of such straight-run gasoline together withheating oil or any other low-boiling distillate fraction which is notintended to be utilized for further processing, as later described.

Unvaporized liquid separated in separator Il is removed from the bottomthereof through line 2| and may be discharged through line 22 to afurther heating coil or other equivalent heating device wherein it israised to a higher temperature for effecting further vaporization. Forexample, according to one phase of the present invention, the oil duringpassage through the heating coil 23 may be raised to a temperature offrom '700 i F. to 850 F. In cases where the temperature of the oil israised above active cracking temperature, the heating be sufficientlyrapid to avoid any substantial amount of thermal cracking therein. Theproducts from the heating coil 23 are then discharged throughtransfer-line 24 into a separator 25 in which additional vapors formedduring the heating v.may separate from unvaporized residue.

In some cases, the oil from the bottom of the primary separator I4hereinbefore described may the vapors formed during the within thefurnace 23 should be passed directly to the catalytic cracking zonewithout being subjected to further heating, and, according to anotheralternative, preheated products from the coil 23 may be passed directlyto the cracking zone without intermediate separation of vapors andliquid, as later described.

Returning again to the separator 25, when operating in this mannervapors liberated therein are removed overhead through line 23 into.which is introduced a finely-divided adsorptive cracking catalystthrough conduit 21. This cracking catalyst may be any suitableadsorptive material capable of effecting or modifying the crackingreaction, such as. for example, acid-treated or other activated clays,synthetic gels of silica and alumina, silica and magnesia, alumina' andboron oxide, and the like. 'I'he size of the cata lyst particlesintroduced into the gas stream passing through line 26 should be such asto permit the gas stream carrying the particles into the cracking zoneand may vary over an extended range, such as from`30 mesh to 400 mesh orfiner. The suspension of oil vapors and catalyst formed by theintroduction of the catalyst into the oil vapor stream then passesthrough line 29 into the bottom section of a reaction chamber 29 which,for illustrative purposes, has been shown in the form of an invertedcone through which the oil vapors are passed in an upward directionagainst the force of gravity.

Returning to the secondary separator 25, un-

vaporized liquid is removed from the bottoml thereof through line 3l andmay be passed through lines 32 and 33 and combined with the suspensionof oil vapors and catalyst passing to the inlet of the reactor 29.Instead of combining the liquid residue from the separator 25 with thestream of gases introduced into the reactor, j

it may be desirable in some instances to separately introduce the liquidstream into the reactor. To this end, a part or all of the liquidflowing through line 3 2 may be passed through wardly through reactionchamber 29 is controlled so as to form a relatively dense phase ofcatalyst and gases within the major portion of the reaction chamber. Byproperly proportioning the diameter of the cone forming the wall of thereactor 29, the velocity of the vapors passing therethrough may bereduced to such a point that the bulk of the catalyst particles settlesout of the oil vapors before the latter are removed from the crackingchamber. When operating in this manner, a bed of finely-divided catalystis built up within the reaction chamber 29 which is continuouslysubjected to violent agitation by the current of rising vapors passingtherethrough. As a result, a substantially uniform temperature may bemaintained throughout the entire length and breadth of the reactionzone.

The Vamount of catalyst present in the reaction zone should besuillcient to completely absorb all liquid constituents introducedtherein through lines 33 or 34 so as to avoid the formation of a tion ofthe catalyst particles and give rise to operating di-lculties, Thedensity of the catalyst bed withinthe reaction chamber 2li-may, forexample, be between l and 30 pounds per cubic foot when employingactivated clays as a catalyst and the velocity of the oil vapors passingthrough the reaction zone may range from 1 to 10 feet per secondV in thelower section of the cone to from l to 2 feet pei-second in the topsection of the cone. The time of passage. of the oil vapors through thecatalyst bed within the reaction chamber 29 is controlled to obtain thedesired conversion and will vary with the type of catalyst, temperaturemaintained, and other factors. In general, the time of contact of theoil within the reaction zone may be of the order of from 5 to 20 secondsor more. In this connection, it might be mentioned that the liquid oilintroduced into the reaction chamber 29 and absorbed on the catalyst maybe retained within the zone for a period materially greater than thetime of resi- 28. The cracking zone should be maintained at activecracking temperature, such as from 800 F. `to 1100 F.

All of the heat may be supplied to the reaction chamber by the hotregenerated catalyst introduced through line 21, as later described. Insome cases, it may beydesirable to subject either the vapors or theliquid stream passing to the reaction chamber to further heating. Forexample, either the overhead vapors from separator or the liquidbottoms, or both, may be passed through further heating furnaces (notshown) located in lines 26 and 32, respectively.

The cracked vapors and gases after passing through the reaction chamber29 pass overhead through line 31 and may be discharged into a l suitableseparating device such asa cyclone separator 38 for the removal of anyentrained catalyst particles. The entrained catalyst separated by theseparator 38 may be discharged through conduit 39 back into the reactionchamber 29,. preferably below the level of catalyst maintained therein.

'I'he cracked products are removed from the separator 38 through line 4Iwhich leads to a `product fractionator 42 in which the products aresubjected to fractional condensation to condense constituents boilingbelow the desired motor fuel range.

While only one separator has been shown for the removal of the entrainedpowder from the cracked vapors, it may be desirable in some cases tosubject the cracked products to further puriiication before passing tothe product fractionator. For example, the cracked products may bepassed to additional cyclone separators, electrical precipitators, baglters, and the like to effect further purification. l

The cracked vapors passing through the prod uct fractionator 42 aresubjected to fractional condensation to condense the higher boilingconstituents and to segregate the same from the desired motor fuelfraction. Vapors remaining uncondensed and comprising the desired motorfuel fraction together with the lower boiling normally gaseousconstituents formed in the cracking process are removed from the productfractionator 42 through line 43 which leads to a condenser 44 in whichthe desired motor fuel distillate is liquefied. Products fromthecondenser 44 may then pass to a product receiver 45 in which theliquid distillate segregates from normally gaseous constituents. Theliquid distillate collected in the receiver 45 is removed therefromthrough 20 dence of the oil vapors introduced through line i 3' line 46as a-nalproduct of the process, This product may be subjected to furtherstabilizing, refining and finishing treatment for the production of thenal market product. AIf desired, -a portion of the distillate removedfrom the receiver 45 may be pumped back through line 4l and pump 48 tothe top section of the fractionating tower 42 as a reflux mediumtherefor.

The normally gaseous constitutents separated from the liquid distillatein the receiver 45 are removed overhead through line 49 and may berejected from the system through line 59 which may lead to suitableabsorption or other equipment for further drying and puriiication. How#ever, according to one of the phases of the present invention, a portionof this gas formed may be returned to the cracking zone and employed asa carrier for the catalyst. as later set forth.

During the cracking process the catalyst contained in the reactionchamber 29 rapidly be comes contaminated with carbonaceous depositswhich reduce the activity thereof and as a result it is necessary tocontinuously regenerate the catalyst in order to maintain the desiredactivity.

Returning to the reaction chamber 29, a conduit 5| may be providedwithin the reaction chamber 29 for the continuous removal of catalystfrom the reaction zone. As i11ustrated,"the conduit, 5| terminates inthe upper section of the reaction chamber 29 at the catalyst level or ata point below the catalyst level so that the catalyst continuouslydischarges into the lconduit and is withdrawn therefrom through line 52.The catalystto be regenerated, which is removed from the reactionchamber through conduits 5I and 52, may .discharge through a controlvalve 52' into a stream oi oxidizing gas introduced through line 53which carries the catalyst through line 54 into a regenerating' chamber55. The regenerating chamber 55 may be of conical shape and of the samegeneral construction as the reaction chamber 29. 'I'he velocity of theoxidizing gas passing through the regenerator 55 is preferablycontrolled to build up a relatively dense phase of catalyst thereinwhich is subjected to constant agitation by the rising stream ofoxidizing gas in a manner similar to that described with respect to thereaction chamber 29.

'I'he passage of the oxidizing gas through the mass of catalyst in theregenerator 55 causes the M burning of the combustible or carbonaceousdeposits formed on the catalyst as a result of the cracking treatment.This burning of the `carbonaceous deposits results in the liberation ofconsiderable heat which causes a rise in the temperature of thecatalyst. In most cases it is necessary to control the regeneratingtemperature below a predetermined value in order to avoid permanentlyimpairing or deactivating the catalyst particles. For example, in thecase of activated clays it is desirable in most cases to maintain theregenerating temperature below a maximum of 1200 F.

The temperature within the regenerating cham- `ber` may be controlled inany conventional manner. For example, suitable cooling elements may bepositioned within or around the regenerating chamber to remove excessheat. As another example, a part of the spent regenerating gas may becooled and recirculated, or a part of the regenerated catalyst may becooled and returned to the regenerating zone. Another method of maintaining the regenerating chamber at the required temperature is to providesumcient solid material therein to absorb all the heatliberated by burn-'ing the combustible deposits without raising the ytemperature above thedeactivating temperature.

As previously described in connection with the reaction chamber 29, theprovision of an inverted conical regenerator permits a reduction in thevelocity of the oxidizing gas passing therethrough and permits thesettling of the bulk of the catalyst from the oxidizing gas within theregenerator 55. The density of the catalyst mass within the regeneratorand the velocity of the oxidizing gas passing therethrough may becontrolled in; the same manner as described with respect to the reactionchamber 29.

Spent regenerating gas after passing through the regenerator 55 isremoved therefrom through line 50 from whence it may -be introduced intoa suitable separating device such as a cyclone separator 51 for theremoval of any entrained catalyst present therein. The entrainedcatalyst separated in the separator 51 may discharge through conduit58`back into the regenerator 55. After passing through the separator 51,the spent regenerating gases may be rejected from the system throughline 59, or it may be passed to other suitable purification and heatrecovery equipment which, for simplicity, has not been shown in thedrawing.

'I'he catalyst after being subjected to the desired degree ofregeneration within the chamber 55 is removed therefrom through acentral conduit 6l which has an open end terminating at or below thelevel of the catalyst bed within the regenerating chamber. Theregenerated catalyst collected in the conduit 6I discharges into thevertical conduit 21 from whence it is discharged at the desired ratethrough control valve 62 into the stream of gases in line 2S.

Since the regenrating temperature is usually considerably above thedesired cracking temperature, a substantial amount of heat for carryingvout the cracking treatmentI may be supplied by hot catalyst from theregenerating zone and the amount of heat supplied from this source'maybe regulated within limits by the amount of hot regenerated catalystmixed with oil vapors and the relative temperatures employed forcracking and regeneration. Y

In order to circulate the catalytic material through the reaction andregenerating chambers,4

it is necessary to build up a suiiicient pressure on the catalyst tofeed the same into the gaseous streams passing to the reactionand-regenerating chambers. These gaseous streams must in turn be undersufficient pressure to overcome the pressure drop through the equipment.For example,

tbe-gas stream passing into the reaction chamber 23 should be undersufilcient pressure to force the oi'l vapors through the reactionchamber and the subsequent separating, fractionating and reningequipment. The pressure drop through the cracking and fractionatingsections of the equipment may be, for example, of the order of from 5 to25 pounds per square inch. On the other hand, pressure of the air oroxidizing gas passing through lines 53 and 54 to the regenerator 55 mustbe under suificient pressure to overcomethe pressure drop through theregenerating chamber and the subsequent recovery equipment. Thispressure drop may be of the order of from 2 to 20 pounds per squareinch. As a result, sufficient pressure must be built up on the catalystto return the same from the outlet of the regenrator' to the inlet ofthe cracking chamber and from the outlet of the cracking chamber to theinlet of the regenerating chamber. Any suitable means may be providedfor building up the requircr. pressure, such as by means of double bellhoppers, compression screws, feed pumps, and the like. As illustrated,the conduits 52 and 21 employed for feeding the catalyst from thereaction chamber to the regenerating gas j stream and from theregenerating chamber to the oil vapor stream. respectively. are of suchheight as to develop sumcicnt static head to overcome the pressure dropthrough the system. In order to develop t c static head of pressure inthe conduits 21 'and 52, the catalyst therein should be maintained in afreely flowing state. To this end, a iiuidizing gas may be introduced atone or more spaced points along vthe conduits. Such fluidizing gas mayalso serve to Purge or strip spent catalyst of volatile hydrocarbonsretained on the catalyst.

According to the process previously described, which constitutes thepreferred embodiment of the invention, the oil vapors liberated in theseparator 25 are utilized as a carrier for transferring the catalystfrom the regenerator into the reaction zone. As previously mentioned,however, the

4present invention contemplates the use of other passed through line 83to compressor 54 which y builds up sufllcient pressure on the gases toforce the same through line 65 to line 23 into which the regeneratedcatalyst is injected through line 21. When operating in this manner, thesecond separator 25 may be omitted and the total products from theheating coil 23 may be passed through line 66 which merges with line 32leading to the inlet line 23 through line 33 or the reactor 23throughline 34.

Instead of employing the residual gas from the process for carrying thecatalyst from the regenerating chamber back to the reaction chamber, anextraneous gas, such as nitrogen, hydrogen,

I carbon dioxide, and the like, may be introduced through line 51 whichmerges with line 65 which in turn merges with line 26.

When employing off gases from the cracking The process hereinbeforedescribed contem' plates the employment of a total crude containing asubstantial quantity of straight-run gasoline as a feed stock for theprocess. In cases where reduced crudes or topped crudes are available,or in cases where the total crude contains only a small quantity ofstraight-run gasoline, preheating coil i2 and separator I4 may beeliminated. For example, a topped crude, reduced crude or a total crudecontaining a small fraction of gasoline may be introduced into thesystem through line 63 rather than line I0. This feed introduced throughline 69 may be forced by means of pump Il to the heating coil 23 inwhich it may be preheated before passing the same to the cracking zone.

From the above description it will be underl stood that the presentinvention comprehends the processing of heavy oils such as heavydistillates or residual stocks without intermediate vaporization beforecontacting the same with the catalyst material and in which the catalystmate.- rial is first suspended in a gaseous stream and introduced intothe reaction chamber.

The use of inverted cone-shaped reaction chambers finds particularapplication in the present process, since the use of steam or othergases to effect complete vaporization of the oil is unnecessary. As aresult, the increase in volume of vapors due to the cracking reaction issubstantially greater than in cases where substantial amounts of steamor other vapors or gases employed to vaporize the feed are present inthe oil vapors.

Having described the preferred embodiment oi' the invention, it will beunderstood that it embraces such other variations and modifications ascome within the spirit and scope thereof.

What is desired to be protected by Letters Patent is:

1. A process for the conversion of higher boiling hydrocarbons intolower boiling hydrocarbons suitable for motor fuel which comprisesintroducing hot finely-divided absorptive cracking catalyst into astream of oil vapors to be cracked to form an oil vapor-catalystsuspension, thereafter combining with said suspension a stream of oilhaving a substantial portion thereof in liquid form in an unheatedreaction zone whereby heat is supplied directly from the catalyst toeffect the decomposition of the oil and subjecting the resulting mixtureof oil and catalyst to cracking conditions to convert a substantialportion of said oil into lower boiling motor fuel constituents,thereafter separating the cracked products from the catalyst andsegregating a motor fuel fraction therefrom.

2. A process for the conversion of higher boiling hydrocarbons intolower boiling hydrocarbons suitable for motor fuel which comprisespreheating the hydrocarbon oil to be converted to vaporize a substantialportion thereof and to retain another portion in unvaporized condition,separating the vapors from the unvaporized liquid, mixing with saidvapors a hot nely-divided absorptive cracking catalyst to form acatalystvapor suspension, thereafter mixing with said hot suspension astream of the unvaporized oil, subjecting the resulting mixture tocracking conditions of time and temperature in an unheated reaction zoneto form a substantial portion of lower boiling hydrocarbons suitable formotor fuel, providing suiicient catalyst within said cracking zone tosupply heat to effect the reaction and completelyy absorb unvaporizedliquid hydrocarbons to thereby form a relatively dry mixture of crackedvapors and catalyst, thereafter separating the cracked vapors from thecatalyst, segregating a motor fuel product from the cracked products.regenerating the catalyst by removing combustible deposits formed onsaid catalyst during the cracking treatment and combining hotregenerated catalyst directly with said firstnamed hydrocarbon vapors.

3. In the process dened by claim 2, the further improvement whichcomprises gradually reducing the velocity of the oil vapors passingthrough the cracking zone to maintain said cracking catalyst within saidzone for a period materially greater than the time of residence of theoil vapors therein.

4. An improved process for converting dimcultly vaporizable oils-intolower boiling products which comprises preparing a dense suspension of ahot, finely divided catalyst in a completely vaporized hydrocarbondistil1ateadmixing a stream of said suspension with the heavier oil,which is incompletely vaporizable without decomposition, in a verticalreaction zone wherein the catalyst is maintained in a iiuidizedcondition, maintaining the reaction zone at the decompositiontemperature by heat supplied from the catalyst and providing timetherein to eiect the decomposition of the heavier oil with deposition ofcoke on the catalyst" and withdrawing streams of fluidized o catalystfouled with coke and vaporized cracked

